From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 298522E54A3 for ; Thu, 23 Apr 2026 01:36:57 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776908218; cv=none; b=tZWQ6hrQ3fHqgUyWfaa6BA0Ef4vHjWseJfq34B5EY+aYBYj+jvSkln5IuPTfd6m1WhmXRssGLKokliQJa1dFRtU9szF+B2HPQIdMAwXMJm5k2tDOzLsoD4d4WlHwazIkqqOSQAj6O9BbP3XNmNUK5P7tu50TQN/6CdVpUjIgI4E= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776908218; c=relaxed/simple; bh=5ophnTHEismmvQWNDghkIVI1SEYQ74JbW+R8huYXPOg=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=bFkDer0M9HxRjeGLH33uIzTNrGCZqlKVrKVwaOQ/8cZaTOSGozRKOmakfwxHKSE2rSu0FfSL6McEY4N9QdUmX2zJtFpJsOJmZCXOxFnyZxtPaPiRgHSjSP6plJ9DjBMW8dh7tvmzkmCh7f2K+6jtPLJNLnzbHDoJX5/g1FBmnAM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=GpBZ9xFo; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="GpBZ9xFo" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6CCC0C19425; Thu, 23 Apr 2026 01:36:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1776908217; bh=5ophnTHEismmvQWNDghkIVI1SEYQ74JbW+R8huYXPOg=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=GpBZ9xFo4lrMYIv2dAKyfjTO3L6bLC2iCu3G7ON2vbR0UXNKVfoEANFwoO8wK6jYj dHfzZHBRKqFJfJiqqbQj1qm9E4c/TT37ZYF1hTGWv1Dsv3CZ9lud5na2bzE+w4QSRc zljvenWVB3/E4Dre38b3Dl9/sSfu/zN3nSjLMFLAMGfrHosVkymFJTJ8GMS4Lq0uL0 Q7Flq6XNN59TPudpqGyVBUBK6TdeGqyOuKiThb5HDSXdJxnQb3aDupwW0NOAncpptZ RflO7D+IGXpmneLUwhs0WLQsV/ZIRe0lch1K9DNHfAjngAaN8DSJFdyazTBjTn4jLe sx/hSs2pqSFjQ== Date: Thu, 23 Apr 2026 10:36:55 +0900 From: "Harry Yoo (Oracle)" To: "Vlastimil Babka (SUSE)" Cc: Andrew Morton , Christoph Lameter , David Rientjes , Roman Gushchin , Hao Li , Alexei Starovoitov , Uladzislau Rezki , "Paul E . McKenney" , Frederic Weisbecker , Neeraj Upadhyay , Joel Fernandes , Josh Triplett , Boqun Feng , Zqiang , Steven Rostedt , Mathieu Desnoyers , Lai Jiangshan , rcu@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH 1/8] mm/slab: introduce k[v]free_rcu() with struct rcu_ptr Message-ID: References: <20260416091022.36823-1-harry@kernel.org> <20260416091022.36823-2-harry@kernel.org> Precedence: bulk X-Mailing-List: rcu@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Wed, Apr 22, 2026 at 04:41:19PM +0200, Vlastimil Babka (SUSE) wrote: > On 4/16/26 11:10, Harry Yoo (Oracle) wrote: > > @@ -1523,18 +1522,34 @@ kvfree_rcu_bulk(struct kfree_rcu_cpu *krcp, > > } > > > > static void > > -kvfree_rcu_list(struct rcu_head *head) > > +kvfree_rcu_list(struct rcu_ptr *head) > > { > > - struct rcu_head *next; > > + struct rcu_ptr *next; > > > > for (; head; head = next) { > > - void *ptr = (void *) head->func; > > - unsigned long offset = (void *) head - ptr; > > + void *ptr; > > + unsigned long offset; > > + struct slab *slab; > > > > + if (is_vmalloc_addr(head)) { > > + ptr = (void *)PAGE_ALIGN_DOWN((unsigned long)head); > > + } else { > > + slab = virt_to_slab(head); > > + if (!slab) > > + ptr = (void *)PAGE_ALIGN_DOWN((unsigned long)head); > > + else if (is_kfence_address(head)) > > + ptr = kfence_object_start(head); > > + else > > + ptr = nearest_obj(slab->slab_cache, slab, head); > > + } > > It seems a bit wasteful to do this... (especially the virt_to_slab()) part. > > > + > > + offset = (void *)head - ptr; > > next = head->next; > > debug_rcu_head_unqueue((struct rcu_head *)ptr); > > rcu_lock_acquire(&rcu_callback_map); > > - trace_rcu_invoke_kvfree_callback("slab", head, offset); > > + trace_rcu_invoke_kvfree_callback("slab", > > + (struct rcu_head *)head, > > + offset); > > > > kvfree(ptr); > > ... and then throw it all away and let kvfree(ptr) do it again. So maybe we > could then call something more internal and specific based on the result of > the above. Good point, will do. -- Cheers, Harry / Hyeonggon